[clang] [clang-format] Option to ignore PP directives (PR #70338)

[Owen Pan via cfe-commits]

https://github.com/owenca requested changes to this pull request.

Please refer to the [policy](https://clang.llvm.org/docs/ClangFormatStyleOptions.html#adding-additional-style-options) for adding new options.

https://github.com/llvm/llvm-project/pull/70338